Hoist brake



April 7, 1970 v o. M. ULBING 3,504,391

HOIST BRAKE Filed Feb. 7, 1969 5 Sheets-Sheet 1 FIG.

INVENTOR OTMAR M. ULBING ATTORNEY April 7, 1970 o. M. ULBING 3,504,891

1 HOIST BRAKE Filed Feb. 7, 1969 5 Sheets-Sheet 2 FIG. 2

INVENTOR OTMAR M. ULBING ATTORNEY O. M. ULBING' April 7, 1970 HOIST BRAKE 5 Sheets-Sheet 3 Filed Feb. 7, 1969 l l llli 'll/" INVENTOR OTMAR M. ULBING 11M w. PM

ATTORNEY April 7, 1970 o. M. ULBING 3,504,891

HOISI' BRAKE Filed Feb. 7; 1969 5 Sheets-Sheet 4 F/G. LOAD INV OR OTMAR M. U NG ATTORNEY April 7, 1970 o. ULBING 3,504,891

HOIST BRAKE Fileq'Febfv, 1969 5 Sheets-Sheet 5 8 INVENTOR OTMAR' M. ULB/NG Dow-Q) TILE/4M) ATTORNEY United States Patent US. Cl. 254-168 11 Claims ABSTRACT OF THE DISCLOSURE A balancing hoist using a pneumatically displaced piston and having the safety feature of a drum brake automatically actuated by pneumatic pressure if a work load is not attached to the cable when the hoist is operated. The brake is released by the application of a load to the hoist which overcomes the effect of a pneumatic force acting to apply the brake.

Cross-references to related applications This application is a continuation-in-part of my copending United States application, Ser. No. 676,877, filed Oct. 20, 1967, and is related to my copending United States application, Ser. No. 645,644, filed June 13, 1967.

Background of invention This invention relates to hoists and in particular to a pneumatic balancing hoist having an automatic safety brake arrangement. An example of this type of hoist is disclosed in United States Patent No. 3,286,989, issued Nov. 22, 1966.

Prior art balancing hoists have remote control for the operation thereof to rotate the drum to raise the cable. Unloading positions are provided with such controls to halt drum rotation in the event it is found that a load is not attached to the hoist, or the load is improperly secured, after the hoist drum rotation has been started. Known hoists, then, require a quick action on the part of an alert operator to halt the drum rotation. This is a dangerous limitation; it will often appear that a parcel or load is properly attached to the end of the cable, and yet on operation of the hoist, the hook will travel upward freely, rapidly and unloaded, placing nearby personnel in jeopardy. Quick action by the operator in placing the control in the unload position might prevent an accident when a light load is improperly secured. But where a heavy load is involved, the time required to exhaust the balance chamber would be long enough to permit the hook to travel a considerable distance before the balancing means could respond to the control setting.

Summary of invention The principal object of this invention is to provide a balancing hoist with a fail-safe, automatically-operated, braking arrangement which will halt the rotation of the drum if the load is not properly secured.

Other important objects are: to provide a hoist with a means for locking the hoist against raising movement when the power is suddenly applied to the hoist; to provide a brake is applied by a pneumatic actuator which is sensitive to the load on the hoist cable. The brake is released when the load on the hoist overcomes the braking force of the pneumatic actuator.

Brief description of drawing The invention is described in connection with the accompanying drawings wherein:

FIG. 1 is a cross-sectional, elevational view of the hoist according to the invention less a portion of the trolley support structure;

FIG. 2 is a plan view of the hoist and its trolley support structure, having a portion of the trolley beam and hoist housing cut away;

FIG. 3 is an end view, with the hoist control end cap partly in section, showing the pneumatic channeling and braking arrangement;

FIG. 4 is a perspective view showing the hoist support means and brake linkage in isolation;

FIG. 5A and 5B are functional representations of the two modes of operation of the novel hoist support means;

FIG. 6 is a vertical section through the drum taken along the lines 6-6 in FIG. 7 and showing a modified brake means.

FIG. 7 is a fragmentary vertical section taken along the line 77 in FIG. 6; and

FIG. 8 is a fragmentary horizontal section taken along the line 88 of FIG. 6.

Description of preferred embodiments In FIG. 1, index number 1 is the piston side end cap, 2 the cylindrical frame member and 3 the control side end cap. The control end cap carries ball nut 4 which is keyed against rotation by #key 5. Ball screw 6 turns in ball nut 4 and supports cable drum 7 held by bolt 8 and keyed against rotation. by key 9. Piston 10 acts upon the drumnut assembly through thrust bearing 11.

Packing 12 seals the piston 10 against the cylinder 2. Cable shield 13 prevents the cable 14 from jumping out of the drum groove 15, and groove 16 in the shield permits insertion of a ball 17 swaged to the end of the cable 14. This ball 17 is received in slot 18 of the cable drum 7 and anchors the cable 14. Cable replacement, therefore, can be made without disassembly of the balancer.

It is my teaching to use a ball nut 4 and ball screw 6 to rotate and translate the drum 7, in which the ball nut is held stationary and the ball screw turned therein and out. While it would seem immaterial whether the one or the other of the elements is rotated, a heretofore unexpected benefit arises in stabilizing the ball nut 4 and turning the ball screw 6. For one, it is not necessary to penetrate the piston 10 with the ball screw 6, and then have to be involved with sealing along the penetration. Rather, the screw 6 is fixed to and carried by the drum 7; the screw terminates within the drum, leaving intact the surface of the piston 10, and translates therewith. Further, the loading of the ball nut 4 is always thereacross. Never does the loading, via the paying-out of cable 14, get beyond the ball nut, before the ball nut, or behind it. Load ing always occurs across the same cross-sectional area of the ball nut, thus the ball nut is never met with variably-displaced, fore and aft loading stresses. This novel feature greatly enhances the life and maintenance of the two, interacting threaded components.

The support system of the hoist, seen best in FIGS. 2, 3, and 4 consists of bar 19 supported in rubber bushing 20 in both end caps 1, 3, trolley side plates 21 and 22 held at their one end by bar 19 and at their other end by tube 23 having a bar 24 contained Within. One end of bar 24 is held by a rubber bushing 20 While the other end rests against a diaphragm assembly 25. At the approximate center of bar 24 a spherical bushing 26 provides a connection between the bar 24 and tube 23. Pressure chamber 27 above diaphragm 25A is connected to balancing chamber 28 through passages 29 and 30, area 31, and passage 32. Adjustable push rod 33 interfaces bar 24 and bell crank 34. Bell crank 34 is fastened to cam shaft 35 which, as illustrated in FIG. 4, actuates brake shoes 36 by means of cam 37. Pin 38 anchors the opposite end of the brake shoes, and springs 39 hold the brake shoes in a retracted position. Collar 40 in conjunction with a ball fastened to the end of the cable 14, serves as an up stop. Passage 32 formed in cylindrical member 2, and opening in the balancing chamber 28, connects the control end of the hoist with the balancing chamber 28 and communicates the control end thereof with passages 29 and 30.

In the event the load is not properly secured, or the pendant button is accidentally moved to the load or balance position with out any load being secured to the fixture, diaphragm 25A, which is exposed to the same pressure as is in the balancing chamber 28, will flex toward bar 24, as shown in FIG. A. In flexing under the pressure, diaphragm A lifts the corner of the end cap 3 relative to the bar 24, thereby displacing bar 24 and push rod 33 relative to the end cap 3, which actuates brake cam 37, thus engaging the brake by moving shoes 36 outwardly to lock the drum 7 against which they move, as best seen in FIG. 1, against rotation. This chain-reaction linkage is shown in FIG. 4. In order to release the brake the pendant control must be moved to the exhaust position so as to depressurize the balancing chamber 28 and pressure chamber 27. The operation can then be re-started when a proper load is secured to the cable 14.

The contribution of the novel trolley suspension arrangement toward the automatically-operated, fail-safe brake is shown in FIGS. 5A and 5B. The over-head trolley suspension, via the coaxial tube 23 and bar 24 is shown together with diaphragm 25A. The representation in FIG. 5A shows the mode of operation with the hoist in load or balance operating condition with no load secured to the cable. Bar 24 maintains its equilibrium undisturbed, as no loading is placed upon it. However, as previously explained, pneumatic pressure P is passed to diaphragm 25A to displace bar 24. Bar 24 effects a relative R movement downward at the one end, relative to the end cap 3, pivoting on fulcrum F (bushing 26). Bar 24 displaces pushrod 33, and in turn, the brake is engaged. Actually, the diaphragm 25A lifts the R end of the hoist relative to the bar 24. When a proper load is aflixed, the hoist trolley suspension arrangement functions in a different mode so as not to engage the brake.

FIG. 5B shows the disposition of the hoist with a proper load attached. Part of the loading on the hoist bears down on the diaphragm 25A, causing it to bear down on the bar 24. The force bearing down on the diaphragm 25A and the R end of the bar 24 will be only a portion of the total load on the cable 14 since this load is distributed to both ends of both bars 19 and 24. The pneumatic pressure P disposed against the diaphragm 25A is without effect as it cannot overcome the load force bearing down on the diaphragm. Accordingly, the push-rod 33 is not moved, and the brake remain released. In particular, the diaphragm 25A is small enough that the pressure P cannot create suflicient force to overcome the downward force of the load on the diaphragm 25A.

Pneumatic supply is provided to the hoist by input piping 41 (FIG. 3). The pressurized supply is passed to a regulator 42, by way of channel 43, and to a check valve 44 by way of channel 45. The regulator 42 may be any suitable fluid pressure regulator, such as the series 2000 Air Volume Booster manufactured by Fairchild Stratos, W. Babylon, New York. Such regulators have an input, output, and a pilot pressure or biasing control. Accordingly, in this preferred embodiment of my balancing hoist, channel 43 is the input means; a channel 46 communicating with area 31 is the output means; and further channel 47 provides for the pilot pressure. Channel 47 branches from a passageway 48; this latter passageway communicates channel with a pendant control line 49, via a channel 50 which opens on check valve 44 and needle valve 51. Finally needle valve 51 meters between channel 45, channel 47 and passageway 48 communicating therebetween. The needle valve 51 regulates the flow of pressurized fluid; a pendant (not shown) controls the level of pilot pressure addressed to regulator 42. Needle valve 51 is used, and adjusted, to vary the rate of pressure riseand therefore determines the reaction time of the hoist. That is, the rate of fluid flow through needle valve 51 determines the time required to produce the volume of pressure at which a selected pendant relief valve is set to open. Said volume is that at which the hoist balances the load.

On review of FIG. 3, pneumatic piping 41 introduces pressurized air to regulator 42 via channel 43. The regulator output is passed to area 31, via channel 46, where it passes through passageway 32 to the balancing chamber (28, FIG. 1) to operate on the piston (10, FIG. 1). Also, pressure chamber 27 above diaphragm 25A receives the same pressure via passageway 30 as that which is in the balancing chamber, in area 31 and chamber 27. Pilot pressure or biasing pressure is addressed to the regulator, to control same, via channel 45, check valve 44, channel 50, needle valve 51, passageway 48, and channel 47. Coupled via control line 49, to passageway 48, is a pendant (not shown) which vents more or less of the pilot pressure, depending upon the setting of two relief valves thereof. Accordingly, the pendant controls the amount of biasing communicated to the regulator 42 via channel 47. The regulator 42, then, determines the amount of pressure addressed to the balancing chamber (28, FIG. 1) and to the pressure chamber 27.

Pneumatic pressure introduced to the hoist balancing chamber 28 is controlled by means of a pendant control and system disclosed in my copending United States applications, Ser. No. 645,644, filed June 13, 1967 and Ser. No. 676,877, filed October 20, 1967, of which this application is a continuation-in-part. This control and system is not disclosed in this application because it does not form a part of the invention claimed in this application.

Second embodiment-FIGS. 6 to 8 The second embodiment shown in FIGS. 6 to 8 uses a positive-lock type of brake means which is operative in only one direction of rotation of the drum 7 as compared to the shoe-type brake means shown in the first embodiment. The operating means for the brake of the second embodiment is identical to that of the first embodiment.

Looking at FIG. 6 the interior of the drum 7 includes a series of circumferentially spaced longitudinally extending notches 55. One circumferential edge of the notch 55 is beveled at 56 while the opposite edge 57 is hook-shaped in cross section. The beveled edge 56 of each notch 55 is located circumferentially in a clockwise direction relative to the notch 55, looking at FIG. 6, while the hookshaped edge 57 is located in the counted clockwise direction.

A brake pawl 58 is pivoted on a bolt 59 mounted on the end of a boss 60 which extends into the interior of the drum 7 from the casing end cap 3. The pawl 58 includes a tang 62 adapted to engage in the notches 55 and to abut the hook-shaped edge 57 of a notch 55 to positively lock the drum 7 against rotating in a clockwise direction, in the direction of raising the hoist cable 14, as shown in FIG. 6.

The brake pawl 58 further includes a tail 63 located on its end opposite from the tang 62 and projecting downwardly from the bolt 59. A spring 64 is interposed between the tail 63 and the nut 4 to urge the pawl to its non-braking position shown in FIG. 6. The spring 64 urges the tail 63 against an eccentric stop 65 fixed on the end of a long bolt 66. The long bolt 66 extends through the integral boss 60, projects from the outer face of the casing end cap 3 and carries a lock nut 67 for locking the bolt 66 in an adjusted position- The bolt 66 is adjustably rotated to vary the position of the eccentric stop 65. Preferrably, the eccentric stop 65 is adjusted so that the pawl 58 will be located in its released position slightly clear of the interior of the drum, where it is in a position to lock the drum 7 with very little movement.

The pawl 58 is moved to a braking position, clockwise as shown in FIG. 6, by the movement of the bell crank 34 in the same manner as in the first embodiment. The bell crank 34 is attached to the cam shaft 35 pivoted in a boss 69. The boss 69 extends longitudinally into the drum 7 and is integrally attached to the inside of the end cap 3. The inner end of the cam shaft 35 carries a semiarcuate arm 70 which arches over the nut 4 and terminates in a pin 71 engaging in a slot 72 formed in the brake pawl 58. Looking at FIG. 6 a counter clockwise movement of the cam shaft 35 drives the brake pawl 58 in a clockwise direction to engage the tang 62 in a brake notch 55.

As soon as the pawl tang 62 slightly enters the interior of the notch 55, the clockwise movement of the brake drum 70 will serve to pull the pawl 58 into full locking position, in a hook shaped edge 57 of the notch 55. In this position, the drum is positively locked against further clockwise movement in a direction raising the cable 14. Since the brake notches 55 are beveled on the edge 56, any movement lowering the cable 14 will automatically disengage the brake pawl 58 due to the tang 62 being cammed out of the brake notch 55 by the beveled or inclined edge 56. Hence, the brake means shown in the second embodiment is unidirectional, braking only in the direction of the upward movement of the hoist cable 14.

While I have described my invention in connection with specific apparatus, it is to be clearly understood that this is done only by way of example and not as a limitation to the scope of my invention.

I claim:

1. A hoist including:

a frame supporting a rotatable drum and hoist cable wound on said drum, said drum being rotatable in one direction to wind up said cable and rotable in the other direction to unwind said cable;

means on said frame operative to cause said drum to rotate in said one direction to wind up said cable;

brake means operative, when actuated, to hold said drum against rotation in said one direction; and

brake actuator means responsive to the load on said cable and operative, when the load is removed from the cable, to actuate and cause said brake means to hold said drum from winding up said cable.

2. The hoist of claim 1 wherein;

said brake means is ineffective to hold said drum from rotating in the other direction to unwind said cable.

3. The hoist of claim 1 wherein:

said brake actuator means includes a pneumatic actuator urging said brake means in the braking direction and a load responsive means urging said brake means in the non-braking direction with a force that varies substantially with the load on said cable.

4. The hoist of claim 3 wherein:

said pneumatic actuator includes a pneumatic diaphragm.

5. The hoist of claim 3 wherein:

said frame is supported on a support by a mounting allowing it to move up and down relative to said support and said pneumatic actuator acts to lift said frame relative to said support.

6. The hoist of claim 5 wherein:

said brake means includes an operating linkage actuated by the relative vertical movement between said frame and said support.

7. The hoist of claim 6 wherein:

said operating linkage is operative to apply said brake means to hold said drum against movement when said frame is lifted relative to said support by said pneumatic actuator.

8. The hoist of claim 3 wherein:

said means operative to cause said drum to wind up said cable is operated by the same pneumatic pressure that urges said brake means in the braking direction.

9. The hoist of claim 5 wherein:

said support is a horizontal bar having one end resiliently mounted in an end of said frame and the other end urged downwardly relative to said frame by said pneumatic actuator.

10. The hoist of claim 9 wherein:

said horizontal bar is balanced longitudinally in a tube on a fulcrum so that it can tilt longitudinally relative to said tube.

11. The hoist of claim 1 wherein:

said drum contains a plurality of notches; and said brake means includes a pawl adapted to enter one of said notches to lock it against rotation.

References Cited UNITED STATES PATENTS 2,082,633 6/1937 Johnstone 188-174 3,260,508 7/1966 Powell 254-168 3,261,589 7/ 1966 Neumeier 254-435 HARVEY C. HORNSBY, Primary Examiner US. Cl. X.R. 

